Conduit and piping systems for conveying fluids, bulk materials and gases are used in a wide variety of applications. Such piping systems may be used in applications involving pipe line, exhaust systems, stationary piping systems, HVAC, slurry line, and the like.
Various components for such systems have been devised to accommodate different fluids, gases and other materials, and to operate in particular environments. For example, some of the components of such systems are fabricated from flexible metal hose, which offers the advantages of durability, flexibility, relatively low cost, and adaptability to various sizes, configurations and materials.
Flexible metal hose is known to interconnect components which move relative to each other. Some of the common configurations of flexible metal hose include spiral-wound, edge-interlocked hose wherein the edges of a strip of sheet metal are interlocked on a hose winding machine to permit limited deflection of the resulting flexible metal hose.
Corrugated flexible metal hose, on the other hand, can be roll-formed or spiral-wound using special rollers, which shape the corrugations in an annular manner. The corrugations provide flexibility and permit a corrugated pipe or hose section to be bent and shaped more easily than a comparable hose section with smooth walls. Moreover, corrugations can permit a hose section to be bent around a relatively tight radius, and can dissipate dynamic stresses associated with the vibration of the components to which the flexible hose section is attached. However, most spiral wound components do not provide a complete seal, especially in high-pressure applications. In such applications, special liners are used to achieve a seal, but this is expensive and complex to manufacture.
Exhaust systems for internal combustion engines are examples of a relatively severe environment in which the operating characteristics of flexible metal hoses can be used. Flexible metal hose sections are often used for connecting the exhaust pipes from vehicle internal combustion engines with manifold mufflers, tail pipes and other exhaust system components. Flexible metal hose sections are commonly used in the exhaust systems of tractors of tractor-trailer truck rigs because of their flexibility, temperature resistance and corrosion resistance when fabricated from suitable materials, such as stainless steel.
Exhaust systems in general, and vehicle exhaust systems in particular, must perform reliably under relatively severe operating conditions, which can include temperature extremes, corrosive environmental factors and dynamic stress loading. Dynamic stresses in an exhaust system can originate from vibrations associated with the engine and movement of the vehicle. Such dynamic stresses include axial, lateral, torsional, and bending forces, which can be accommodated, to some degree, by flexible metal hose with edge interlocking. However, such piping tends to be relatively unreliable. Additionally, use of special liners in spiral wound systems for use in exhaust system applications can be impractical because of the extreme temperature range in which the system must operate.
Corrugated flexible hose sections can have annular corrugations, such as a bellows-type arrangement, where the corrugations are disposed perpendicular to a longitudinal axis of the pipe. Such bellows-type configurations tend to be relatively efficient at dissipating vibrational energy along their entire lengths. Such annular bellows-type corrugation provides relative movement with five degrees of freedom, namely, 1) compression and extension along a longitudinal axis of the pipe or the “x-axis,” 2) upward and downward lateral offset within the “x-y” plane, 3) leftward and rightward lateral offset within the “x-z” plane, 4) bending about the “y-axis” and 5) bending about the “z-axis.”
However, piping with annular corrugations do not tolerate torsional or twisting forces about the x-axis. For example, some exhaust systems of internal combustion engines, and in particular, truck exhaust systems, have used annularly corrugated pipe couplings to connect various components. However, such systems tend to fail prematurely when subject to repetitive torsional stresses. Repeated dynamic torsional forces can lead to premature metal fatigue. When such systems begin to fail, leaks develop, which may pose a health and safety hazard, in addition to degrading engine performance. Total failure of the system results in physical separation of piping components.
It is desirable to have a flexible pipe coupling that permits movement in six degrees of freedom, including torsional or twisting movement, and which is economical to manufacture and is not susceptible to leaking.